An intake silencer for a gas turbine has been known since the past (refer to, for example, Patent Gazette 1), in which the intake silencer is disposed in a sealed flow path of the intake side of a gas turbine, and is configured by a sound-absorbing splitter group in which a plurality of panel-shaped sound-absorbing splitters including a sound-absorbing material therein is disposed in parallel along a gas flow direction.
Conventionally, an intake silencer used in a large gas turbine specifically has a noise reduction structure configured by a unitary sound-absorbing splitter in which only steel sound-absorbing splitters with a thickness of 200 millimeters are disposed in parallel along a gas flow direction. Because the sound-absorbing splitter with a thickness of 200 millimeters reduces noise mainly at frequencies from 500 Hz to 1 kHz that do not match the dominant frequency 2 kHz of the gas turbine intake noise, noise cannot be efficiently reduced.
Moreover, when a required amount of noise reduction is increased, the length of the sound-absorbing splitter is increased to reduce the dominant frequency 2 kHz of the gas turbine intake noise. As a result of the length of the sound-absorbing splitter being increased, noise at frequencies 1 kHz and below that does not require a very large amount of reduction is unnecessarily reduced, causing needless noise reduction.
As described above, the conventional intake silencer has disadvantages, in that noise reduction efficiency is poor because of the mismatch in noise frequencies to be reduced, size is increased as a result of the length simply being increased based on the amount of noise reduction, and the intake silencer is heavy because the entire splitter is made of steel.
The main components of the intake noise generated from the gas turbine are a fundamental frequency generated by the rotation of a compressor in the gas turbine and its overtones. These frequencies are dominant compared to other frequencies. The fundamental frequency is determined by the rotation frequency multiplied by the number of blades. In the gas turbine, the rotation frequency is high and the number of blades is large. Therefore, the fundamental frequency is a high frequency (for example, 3600(rpm)×36(blades)/60=2160(Hz)).
The intake noise generated at the suction opening of the gas turbine differs depending on the type and capacity of the gas turbine. However, an approximate noise level within a duct is from 120 dB(A) to 130 dB(A).
As many equipments of the gas turbine are installed outdoor, the acceptable noise level for areas surrounding the equipments is 85 dB (A) in terms of working environment, so the intake silencer is required to reduce a large amount of noise, from 35 dB(A) to 45 dB(A).    Patent Gazette 1: Japanese Patent Laid-open Publication No. 2004-28107